As an example of a mobile-object-holding tool mounted in place of a track body on a mobile object which moves along the track body, Patent Document 1 describes a ball slideway mounted on a linear guideway (slider block).
This ball slideway has a constitution in which a pair of holding parts which hold balls and a U-shaped type elastic piece which biases the pair of holding parts away from each other are provided and the separation from the linear guideway is prevented by compression when it is mounted on the linear guideway.